Adhesion of restorative materials to the tooth structure has revolutionized the approach of dental treatment and is now essential for numerous elective dental procedures and for the replacement of tooth substance lost by caries or tooth fracture. Although there have been significant advances in dental adhesion technology, the contribution of dentin extracellular matrix (ECM) molecules to dentin bonding is still poorly understood. Fibrillar type I collagen is the predominant matrix component in dentin, and the maintenance of its fibrillar structure upon etching is crucial for the adhesion between restorative materials and dentin. The mechanisms for the maintenance of the structural integrity, however, are unknown. Based on our preliminary studies, we hypothesize that Chondroitin sulphate (CS-) and Keratan Sulphate (KS-) glycosaminoglycans (GAGs) carrying proteoglycans (PGs) facilitate dentin adhesion by maintaining the spatial architecture and stability of collagen fibrils. To address this hypothesis, the following specific aims are proposed: 1. To evaluate, after the dentin is demineralized, the effects of CS-, KS- or CS-KS removal on: 1a. Morphology of collagen fibrillar structure and collagen cross-linking analysis 1b. Ultimate strength of demineralized dentin and bond strength of adhesive resins 2. To determine, upon rewetting, the contribution of CS- and KS- GAGs/PGs by: 2a. Quantifying the levels of collagen re-expansion, collagen cross-linking analysis, and morphology of fibrillar structure, with and without CS, KS or both GAGs/PGs removal. 2b.Quantifying the UTS and bond strength with and without CS, KS or both GAGs/PGs removal 3. To determine the effects of CS- and KS-GAG addition on collagen re-expansion This combined biomechanical and biochemical approach may provide insights into the roles of CS/KS-PGs in collagen stabilization and dentin adhesion.